Process for producing a groove-like recess, and a groove-like recess of this type

ABSTRACT

The invention describes a process for producing a groove-like recess which is part of a strip seal between two components which enclose a gap, using a material-removing process technology to create the groove-like recess in the two components in such a manner that the groove-like recess in each of the two components, after orientation with respect to one another, lie substantially opposite one another in an end position in which they enclose the gap between them, and that a strip element can be introduced into the groove-like recesses in such a manner that the strip element at least partially projects into both groove-like recesses and, under the action of a force, forms a substantially gastight join with the groove-like recesses in the two components. Furthermore, the invention describes a groove-like recess of this type as part of a strip seal.  
     The invention is distinguished by the fact that the material-removing process technology is carried out in at least two successive steps, namely in a first step in which material is removed at a first material-removal rate and in a subsequent second step, in which material is removed at a second material-removal rate, and that the first material-removal rate is greater than the second material-removal rate.

TECHNICAL FIELD

[0001] The invention relates to a process for producing a groove-likerecess which is part of a strip seal between two components whichenclose a gap, using a material-removing process technology to createthe groove-like recess in the two components in such a manner that thegroove-like recess in each of the two components, after orientation withrespect to one another, lie substantially opposite one another in an endposition in which they enclose the gap between them, and that a stripelement can be introduced into the groove-like recesses in such a mannerthat the strip element at least partially projects into both groove-likerecesses and, under the action of a force, forms a substantiallygastight join with the groove-like recesses in the two components. Theinvention also describes a groove-like recess of this type as part of astrip seal.

PRIOR ART

[0002] Strip seals of the generic type described above are used inparticular in gas turbine technology, in order to preferably completelyeliminate leakage flows which occur through the gap between twocomponents arranged directly adjacent to one another.

[0003] The explanations given below relate to a specific application ofa strip seal within a gas turbine, but it should be noted at this pointthat strip seals are used in a wide range of other application areas, towhich the following statements can readily be transferred.

[0004] U.S. Pat. No. 5,531,457 has disclosed a strip seal arrangementwhich is used to seal two adjacent gas turbine blades or vanes in orderto delimit the volume of the hot-gas passage in a gastight manner from acooling air volume located below the blade or vane roots. The rotorblades or guide vanes which are arranged in large numbers over thecircumferential direction of a rotor or stator arrangement project intowhat are known as securing grooves, in order for them to be secured bymeans of their roots, and as a result adopt a fixed position relative tothe gas turbine blades or vanes which are in each case arranged adjacentto them. For cooling purposes, the individual gas turbine blades orvanes are supplied with highly compressed cooling air, which isgenerally branched off from the compressor stage of the gas turbineinstallation via bypass lines, from the sides of their roots. Most ofthe incoming air supplied passes into a cooling passage system which ismachined into the gas turbine blade or vane and provides cooling passageopenings in the region of the respective blade or vane roots in order tofeeding cooling air. However, cooling air losses occur at thoselocations at which, between two gas turbine blades or vanes arrangedadjacent to one another in a row of blades or vanes, there is a gapbetween the turbine blades or vanes which preferably adjoin one anotherin the root region. Although it is known that leakage or loss flowswhich occur through gaps of this type can be reduced considerably byminimizing the gap width, a tight fit of this type between two adjacentgas turbine blades or vanes leads to mechanical constraints which areassociated with considerable material stresses in particular on accountof the high thermal loads and the thermal expansion of the materials.

[0005] An alternative, effective seal which is also gentle on thematerial is illustrated and described in the abovementioned U.S. Pat.No. 5,531,457, in particular in FIG. 3 of this patent. In this case, theroot regions of two adjacent turbine blades or vanes each provide theopposite, groove-like recesses, into which a strip element projects onboth sides, in order to effectively reduce a leakage flow through thegap enclosed between the two blade or vane roots.

[0006] Hitherto, groove-like recesses of this type have been producedusing erosion techniques which are known per se and allow what are knownas pierced grooves to be introduced. In this context, spark-erosionmaterial-removal processes, in particular cavity sinking by sparkerosion, are particularly preferably suitable, allowing pierced orcountersunk grooves of virtually any desired shape and size to bemachined into the solid material of the blade or vane root. The use oferosion processes leads to a high-quality surface within the groove-likerecess produced using the process, which makes a considerablecontribution to producing a gastight seal by means of the strip elementwhich is introduced in the groove. However, a drawback of erosionprocesses of this type is the very considerable amount of time which isrequired to produce the sealing grooves with a high surface quality andwhich greatly increases costs in particular for industrial massproduction.

[0007] Although alternative material-removal processes are also known,such as for example grinding, which likewise allows good surfacequalities to be achieved within the groove-like recess which can beproduced by the grinding process, grinding processes can only be used atgrooves which are open on the longitudinal side, with a free grooveoutlet. Therefore, countersunk or pierced groove profiles cannot beproduced by means of simple grinding processes. Moreover, the possibleoptions for different shaping in terms of the internal contour in thegroove-like recess or sealing groove are very limited when grinding isused.

SUMMARY OF THE INVENTION

[0008] The object of the invention is to provide a process for producinga groove-like recess, which in particular forms part of a strip sealbetween two components which enclose a sealing gap, using amaterial-removing process in such a manner that, firstly, it is possibleto achieve a high surface quality at the groove surface, which isrequired in order to produce a desired gastight seal, and secondly thematerial-removing process used also allows industrial mass productionwith considerably reduced production costs, i.e. with much shorterprocess times.

[0009] A further object is to provide a groove-like recess whichsatisfies the above requirements and in particular has an optimizedsealing action.

[0010] The solution to the object on which the invention is based formsthe subject matter of claim 1. Claim 14 relates to a groove-like recesswhich is formed in accordance with the invention as part of a strip sealwhich, in a particularly preferred application as described in claims 16and 17, is used in turbo machines, in particular gas turbineinstallations.

[0011] According to the invention, a process for producing a groove-likerecess in accordance with the preamble of claim 1 is carried out in sucha manner that the material-removing process technology is carried out inat least two successive steps, namely in a first step in which materialis removed at a first material-removal rate and in a subsequent secondstep, in which material is removed at a second material-removal rate,and that the first material-removal rate is greater than the secondmaterial-removal rate. Unlike in the previous known way of producing agroove-like recess which is to be introduced into a component and whichis part of a strip seal, in which the groove-like recess is obtainedwith the aid of an erosion process which produces a high surface qualityof the groove, according to the invention removal of material is carriedout in two steps, of which a first step involves removing material asquickly as possible by what is known as roughing, producing a machinedsurface which has a slightly lower surface quality, which cannonetheless deliberately be accepted. Only in a subsequent second stepis material within the groove-like recess which already exists removedby means of a finishing operation using a material-removal processwhich, although it has a slower material-removal rate, leads to a muchhigher surface quality, as is the case, for example, with the erosionprocess which is known per se.

[0012] According to the invention, it has been recognized that, in orderto avoid unnecessarily long process times during the production of theabovementioned groove-like recesses, material can be removed at highmaterial-removal rates in groove regions which do not come into contactwith the strip element during the subsequent sealing action. Only thecontact regions between the strip element and the groove-like recesseshave to be produced with a high quality, i.e. with minimum possiblesurface roughness, since these contact regions make a decisivecontribution to the gastight seal.

[0013] In principle, it is possible for all material-removal processesto be used for the rapid removal of material, for example milling,grinding or erosive roughing processes, with which, depending on thework flow, it is possible to achieve removal rates of 600 cubicmillimeters per minute and above for the machining of surfaces with alower surface quality.

[0014] To remove material in the second process step, i.e. to create thehighest possible surface qualities, the erosive finishing process isparticularly suitable, either allowing finished-machining of a firstmaterial surface which has already been produced by the previousmaterial-removal step or producing new material surfaces withparticularly good material surface qualities by the fresh removal ofmaterial.

[0015] Of course, it is also possible to use more than two process stepsto remove material, these steps each differing with regard to the levelof their material-removal rates and the surface qualities which can beproduced therewith. It is advantageous to start by usingmaterial-removal processes which achieve the highest possiblematerial-removal rates. Then, in the further steps material-removalprocesses which are able to produce ever better material surfacequalities are used.

[0016] The groove depths and groove widths which can be produced usingthe material-removal process and therefore fundamentally the grooveshapes which can be produced can be designed in virtually any desiredsize and shape in particular when erosive removal processes are used.

[0017] Particularly advantageously, the groove width of the groove-likerecess is dimensioned even at its narrowest point in such a manner thatthe narrowest point is greater than the thickness of the strip element,so that to produce a strip seal the strip element projects into bothopposite groove-like recesses on both sides. In this case, the stripelement can move virtually as desired within the mutually oppositegroove-like recesses in the two components. The strip element is onlypressed onto certain regions of the inner contour of the groove-likerecess, known as the contact regions, by the action of an external forcefield on the strip element transversely with respect to its longitudinalextent. Precisely these contact regions are created with a particularlyhigh surface quality, i.e. the lowest possible surface roughness. Bycontrast, all the other groove surface regions can have lower surfacequalities.

[0018] The abovementioned force field which acts on the strip elementwithin the groove-like recesses is in the present example brought aboutby the pressure difference prevailing radially with respect to the bladeor vane extent between the cooling volume and the hot-gas passage whichis oriented radially with respect to the blades or vanes. Moreover, thestrip element, if it is mounted within the roots of rotor blades in arotor arrangement, is subject to the centrifugal forces whichadditionally act on the strip element and are superimposed cumulativelyon the force caused by the pressure difference.

BRIEF DESCRIPTION OF THE INVENTION

[0019] The invention is described by way of example below, withoutrestriction to the general idea of the invention, on the basis ofexemplary embodiments and with reference to the drawings, in which:

[0020]FIGS. 1a, b show diagrammatic cross-sectional illustrationsthrough a strip seal between two components which enclose a sealing gap(prior art),

[0021]FIGS. 2a-d show cross-sectional llustrations through groove-likerecesses which have been designed in accordance with the inventionwithin two components positioned opposite one another.

WAYS OF CARRYING OUT THE INVENTION, INDUSTRIAL APPLICABILITY

[0022]FIGS. 1a and b each show a strip seal which is known per sebetween two components 1 and 2.

[0023] The cross-sectional illustrations shown in FIG. 1a and b show twocomponents 1, 2 which lie directly opposite one another and togetherenclose a sealing gap 3. In each case one groove-like recess 4 ismachined into each of the two components 1, 2 and, in a correspondingend position of the two components 1, 2, these recesses preferably liedirectly opposite one another. In the exemplary embodiment shown in FIG.1a, the two groove-like recesses are designed approximately asrectangular countersunk grooves. The embodiment of a strip sealillustrated in FIG. 1b, by contrast, has V-shaped or trapezoid-shapedgroove-like recesses 4.

[0024] A strip element 5, which is formed as a thin strip of sheetmetal, is introduced into the interior of the groove-like recesses 4, ispressed onto the inner contour of the groove-like recesses 4 on one sideby an external pressure difference Δp and forms a preferably gastightjoin therewith.

[0025] To compensate for possible misalignments between the twocomponents 1, 2 with regard to the opposite groove-like recesses 4 andas far as possible to avoid constraints between the individualcomponents 1, 2 caused by thermal expansion, the groove width h ispreferably selected to be greater than the thickness s of the stripelement 5. Moreover, the groove depth of each individual groove-likerecess 4 is to be selected to be as great as possible, so that themaximum possible width of the strip element 5, known as the span a, canbe produced. The greater the span a, the better the sealing effects andservice lives of the overall strip arrangement it is possible toachieve.

[0026]FIG. 2a shows a cross section through two components 1, 2 eachhaving a groove-like recess 4 which has been designed in accordance withthe invention. The groove-like recess 4 has a cross section which isdesigned to narrow in steps as the groove depth increases. The grooveregions 41 and 42 have been produced using an erosive roughing processand each have a low to normal surface quality at their material surface.By contrast, the material surface region 43 has been produced using anerosive finishing process or by subsequent smoothing of the surface bymeans of a deforming or stamping process and consequently has aparticularly smooth surface. The strip element 5 rests flush againstthis very material surface region 43 in order to produce a gastightseal.

[0027] The cross-sectional illustration in accordance with FIG. 2b showsa comparable arrangement of components to that shown in FIG. 2a, exceptthat the V-shaped groove region 41 has been produced using a grindingprocess allowing the highest possible removal of material to beachieved. Furthermore, the groove-like recess 4 has a deeper grooveregion 43, the inner groove surface of which has a particularly highsurface quality. As mentioned above, the groove region 43 has beenproduced using an erosion process, preferably by means of erosivefinishing. The strip element 5, which has a particularly great span andtherefore a particularly good sealing action, lies in this very regionin order subsequently to produce a gastight join.

[0028] Unlike the exemplary embodiments shown above in FIGS. 2a and b,FIG. 2c illustrates a cross-sectional illustration through twocomponents 1 and 2 which each have a groove-like recess 4, but theserecesses are formed asymmetrically with respect to one another. Thespecific geometric design of the groove-like recess 4 is dependent onthe deformations which are to be expected within the groove and/orstipulated tolerances and may quite easily deviate from a symmetricalstructure.

[0029] The groove-like recesses 4 shown in FIG. 2c have also been formedin the manner described above. Therefore, the groove-like recess 4illustrated on the left in FIG. 2c has a material surface which has beenproduced by means of erosion processes in the region 43, and the stripelement 5 rests in a gastight manner on this surface. By contrast, theentire surface 43′ in the groove-like recess 4 illustrated on the rightin FIG. 2c has been formed with a particularly high surface quality aspart of an erosion process. In this case too, the desired surfacequality can be produced by deformation by means of a ram. When thisprocess is used, the surface can be smoothed by means of a stampingoperation, and in this way the desired surface quality can be achieved.By contrast, all the remaining regions of the groove can be of reducedsurface quality and can therefore be produced using processes with afaster material removal rate. These regions can be produced by means ofgrinding or roughing processes.

[0030]FIG. 2d likewise shows a cross-sectional illustration through twogroove-like recesses 4 formed asymmetrically with respect to one anotherwithin two opposite components 1 and 2. It has proven particularlyadvantageous for the transitions 44 and 45 between two material regions41, 42, 43 which have each been produced using different materialremoval processes to be rounded by means of abrasive processes,preferably using sand-blasting, shot-peening or high-pressure waterblasting.

List of Reference Symbols

[0031] 1,2 component

[0032] 3 gap, sealing gap

[0033] 4 groove-like recess

[0034] 41, 42, 43 material surface regions

[0035] 44, 45 transition regions

[0036] 5 strip element

[0037] a span

[0038] h groove width

[0039] s width of the strip element

What is claimed is:
 1. A process for producing a groove-like recess (4)which is part of a strip seal between two components (1, 2) whichenclose a gap (3), using a material-removing process technology tocreate the groove-like recess (4) in the two components (1, 2) in such amanner that the groove-like recess (4) in each of the two components (1,2), after orientation with respect to one another, lie substantiallyopposite one another in an end position in which they enclose the gap(3) between them, and that a strip element (5) can be introduced intothe groove-like recesses (4) in such a manner that the strip element (5)at least partially projects into both groove-like recesses (4) and,under the action of a force, forms a substantially gastight join withthe groove-like recesses (4) in the two components (1, 2), characterizedin that the material-removing process technology is carried out in atleast two successive steps, namely in a first step in which material isremoved at a first material-removal rate and in a subsequent secondstep, in which material is removed at a second material-removal rate,and in that the first material-removal rate is greater than the secondmaterial-removal rate.
 2. The process as claimed in claim 1,characterized in that the material-removing process technology in thefirst step produces a machined material surface (41) with a firstsurface roughness, in that the material-removing process technology inthe second step produces a machined material surface (43) with a secondsurface roughness, and in that the second surface roughness is less thanthe first.
 3. The process as claimed in claim 1 or 2, characterized inthat the material-removing process technology of the second step is usedat least to produce material surface regions (43), within thegroove-like recess (4), at which the strip element (5) forms a gastightjoin with the respective components (1, 2).
 4. The process as claimed inone of claims 1 to 3, characterized in that the groove-like recess (4)has a groove depth along which the groove-like recess (4) has a variablecross section.
 5. The process as claimed in claim 4, characterized inthat the cross section of the groove-like recess (4) decreasescontinuously and/or in steps as the groove depth increases.
 6. Theprocess as claimed in one of claims 1 to 4, characterized in thatgrinding, milling, erosion, laser cutting or water-jet cutting is usedas the material-removing process technology.
 7. The process as claimedin one of claims 1 to 6, characterized in that in the first step anerosive roughing process and in the second step an erosive finishingprocess is used as the material-removing process technology.
 8. Theprocess as claimed in one of claims 1 to 7, characterized in that in thefirst step an erosion process and in the second step a grinding processis used as the material-removing process technology.
 9. The process asclaimed in claim 8, characterized in that the erosion process is basedon spark erosion.
 10. The process as claimed in one of claims 1 to 9,characterized in that the groove-like recess (4) has a minimum groovewidth which is greater than the thickness (s) of the strip element (5).11. The process as claimed in one of claims 1 to 10, characterized inthat an elastically deformable metal strip is used as strip element (5).12. The process as claimed in one of claims 2 to 11, characterized inthat the material surface (41) with the first surface roughness adjoinsthe material surface with the second surface roughness (43) via atransition region (45), and in that the transition region (45) isrounded by means of a material surface-machining process.
 13. Theprocess as claimed in claim 12, characterized in that sandblasting, shotpeening, high-pressure water blasting, stamping or deforming by means ofa ram is used as the material surface-machining process.
 14. Agroove-like recess which is part of a strip seal between two components(1, 2) which enclose a gap (3) and in which the groove-like recess (4)is formed in such a manner that the groove-like recess (4) in each ofthe two components (1, 2), after orientation with respect to oneanother, lie substantially opposite one another in an end position inwhich they enclose the gap (3) between them, and into which groove astrip element (5) can be introduced in such a manner that the stripelement (5) projects at least partially into both groove-like recesses(4) and, under the action of a force, forms a substantially gastightjoint with the groove-like recesses (4) in the two components (1, 2),characterized in that the groove-like recess (4) has at least one firstgroove surface region (41) with a first surface roughness and at leastone second groove surface region (43) with a second surface roughness,and in that the first surface roughness is less than the second surfaceroughness.
 15. The groove-like recess as claimed in claim 14,characterized in that the groove surface region (41) with the firstsurface roughness is arranged inside the groove-like recess (4) in sucha manner that the strip element (5) forms the gastight join with thisgroove surface region.
 16. The use of the groove-like recess (4) betweentwo components arranged within a turbo machine.
 17. The use as claimedin claim 16, characterized in that the turbo machine is a gas turbineinstallation.
 18. The use as claimed in claim 17, characterized in thatthe components (1, 2) are gas turbine blades or vanes, and the stripseal is used to seal the hot passage within a gas turbine from acooling-air volume.
 19. The use as claimed in claim 18, characterized inthat the strip element (5) within the groove-like recess (4) is pressedin a gastight manner onto the respective component (1, 2) by an excesspressure which prevails within the cooling volume compared to thepressure ratios prevailing in the hot passage.